Objective To investigate the value of spectral computed tomography (CT) imaging combined with urinary fibrinogen γ chain (FGG) in differentiating benign and malignant solitary pulmonary nodules (SPN).

Methods From December 2018 to June 2021, a total of 63 (37 malignant and 26 benign) patients with SPN who underwent conventional dual-phase contrast-enhanced scanning using spectral CT were selected as study subjects. The parameters of energy spectrum CT imaging included iodine concentration (IC) of arterial (ICLa) and venous (ICLv) stage lesions; normalized IC (NICa/NICv, normalized to IC in aorta); slope of Hounsfield unit (HU) curve of energy spectrum (λHUa/λHUv) and the monochrome CT number (CT40 keva/v, CT70 keva/v) on 40 and 70 keV images were enhanced. Urinary FGG levels were measured using enzyme-linked immunosorbent assay (ELISA). The diagnostic value of energy spectrum CT imaging combined with FGG in differentiating benign and malignant SPN was evaluated by receiver operating characteristic (ROC) curve.

Results The diagnostic accuracy of energy spectrum CT imaging for malignant nodules was 73.0%(27/37), and was 53.8% (14/26) for benign nodules, the difference was statistically significant (P < 0.05). The diagnostic accuracy of spectral CT imaging for malignant nodules was 73.0%(27/37), and the diagnostic accuracy for benign nodules was 53.8% (14/26), and the difference was statistically significant (P < 0.05). Compared with benign SPN, the CT40 keVa, CT40 keVv, CT70 keVa, CT70 keVv, λHUa, λHUv and ICLv of malignant SPN were significantly decreased (P < 0.05). The median urine FGG level of patients with malignant SPN was 2.210 ng/mL (IQR, 1.780 to 3.120 ng/mL), and was 1.587 ng/mL (IQR, 1.140 to 1.975 ng/mL) in patients with benign SPN, the difference was statistically significant (z=4.264, P=0.014). The diagnostic accuracy of urine FGG for malignant nodules was 73.0% (27/37), and 46.2% (12/26) for benign nodules, the difference was statistically significant (P < 0.05). The area under the curve (AUC), sensitivity and specificity were 0.924, 93.8% and 85.7% for the differentiation of benign and malignant SPN by energy spectrum CT and FGG.

Conclusion Energy spectrum CT imaging combined with urine FGG level detection is beneficial to improve the differential diagnosis efficiency of benign and malignant SPN.